Flotation concentration of potash ores



United States Patent FLOTATION CONCENTRATION OF POTASH ORES James B.Duke, Carlsbad, N. Mex., assignor to Minerals & Chemicals Corporation ofAmerica, a corporation of Maryland No Drawing. Application March 23,1954, Serial No. 418,229

10 Claims. (Cl. 209-466) The present invention relates to the flotationconcentration of potash ores, and more particularly to the flotationconcentration of such ores in two stages whereby there is produced twoseparate concentrates, one of which is a high grade concentrate ofcomparatively finely divided sylvite and the other consistingprincipally of coarser or granular, but somewhat lower grade, sylviteparticularly suitable for use as a fertilizer for which purpose suchcoarser material is essential.

It has long been known that a high grade sylvite concentrate can beobtained by flotation of comparatively fine sylvite from an ore such assylvinite by the use of a long chain aliphatic amine in conjunction witha colloidal material such as solubilized starch and that a coarseconcentrate can be obtained similarly by the use of an amine and fueloil usually by the use of shaking tables. It has not hitherto beenpossible, however, to treat a mixture of coarse and fine sylvinite orewithout first separating it into coarse and fine fractions which is atroublesome and costly operation.

Since coarse sylvite is a valuable fertilizer, various methods have beenemployed for its production, for example finer material is in some casesfused, crushed and screened. Usually, however, coarser sylvinite isseparated from the crushed ore and concentrated separately while thefiner material is treated by flotation.

By coarse sylvinite is meant materiahas coarse as six or eight mesh; byfine sylvite is meant material finer than about 28 mesh and preferablyall finer than about 35 mesh.

I have invented a novel and useful process for simultaneously recoveringa high grade finely divided sylvite concentrate and a lower gradecoarser sylvite concentrate from a sylvinite ore.

The advantages of the process of my invention are the elimination offine grinding of the sylvinite ore which is necessary in the flotationprocess as employed at present, the virtual elimination of a troublesomemiddling product which at present must be returned to the circuit forfurther treatment, the production of two valuable products in a singleflotation apparatus and the production of a valuable fertilizer by asimple method without the need of fusion, etc.

The essential steps of my process comprise 1) coarsely crushing crudesylvinite ore; (2) mixing the coarsely crushed ore with a substantiallysaturated aqueous solution of the soluble constituents of the ore toform an aqueous suspension thereof; (3) substantially removing slimesfrom the aqueous suspension of the ore; (4) subjecting the deslimed oreto flotation using as principal reagents a long chain aliphatic amineand a water insoluble oil thereby producing a floating concentrate ofsylvite particles and a tailing principally consisting of halite whichmay be discarded; and (5) refloating said concentrate after agitating itwith an inorganic colloid material thereby obtaining a high grade finelydivided sylvite concentrate as a floating product and an unfloatedcoarser sylvite product. While it is not essential to my process, it iswithin the scope of my invention to subject the unfloated coarsersylvite product to a screening operation, if desired, to substantiallyremove low grade finer material which may be present therein.

In practicing my invention the crude sylvinite ore is crushed preferablyto about 8 mesh, although good re- 2,706,559 Patented Apr. 19, 1955sults have been obtained with ore crushed only to through 4 mesh orthrough 6 mesh, the overall recovery tending to be somewhat lower,however. The coarsely crushed ore is then mixed with brine, by which ismeant a saturated solution of the soluble constituents (practically allsodium and potassium chlorides) of the ore to form an aqueous suspensionthereof.

Next, slimes are substantially removed from the aqueous suspension ofore by any of the conventional methods, and with suitable apparatus,known to those skilled in the art, thereby to deslime the orepreparatory to flotation. The deslimed ore suspended in saturated brineis then conditioned principally with a long chain aliphatic amine, suchfor example as octadecylamine, or a mixture of such amines, and an inertwater insoluble oil such, for example, as fuel oil, and if desired asuitable frothing agent or other auxiliary flotation reagents. By thismeans, there is obtained a rougher concentrate of the sylvite, theunfloated solid sodium chloride being discarded. In practice the solidsodium chloride is removed by Well known means and the recoveredsaturated brine returned to the circuit for further use.

The rougher concentrate preferably without further addition of theaforesaid flotation reagents, is agitated with an inorganic colloidsuch, for example, as fullers earth or bentonite, in a thick or thinpulp, preferably thin, and then is refloated. In this reflotation step afloating fine concentrate of high grade potassium chloride is removed,leaving a lower grade, coarser material as a tailing.

Finally, this tailing is screened or sized by classification at about 28mesh, the coarser material being suitable for use as a fertilizer whilethe finer material, consisting largely of sodium chloride, may usuallybe discarded as the amount of it is small, or it may be returned to therougher flotation circuit together with new feed; in either case theamount of KCl lost in the operation is reduced to a minimum.

In some cases it is unnecessary to screen the unfloated product, sincethe amount of fine material present is too small to lower the gradebelow that required for a fertilizer product.

It will be understood that the floating high grade concentrate may besubjected to reflotation in order to still further increase its grade,if desired, and unfloated material being screened or classified in thesame way as the original tailings produced in the first reflotation sep.

Asthe inorganic colloidal material used in the second flotation step, Iprefer to use an inorganic colloidal clay, such as fullers earth,bentonite, or the slime removed from the crude ore before flotation.

The amount of colloidal material I have found useful of the order of twoto 20 lbs. per ton of raw feed. To facilitate the understanding of thisinvention, the following examples are given by way of illustration.

Example I A sample of ore from the Carlsbad district of New exico wascrushed to pass an 8 mesh screen and made into a pulp by mixing with asaturated solution of the same ore. The slimes were removed bydecantation and the deslimed ore in the form of a pulp containing 70%solids was conditioned forone minute with reagents consisting of Armac T0.8 lb.; fuel oil 1.47 lbs. and pine oil 0.2 lb.; all per ton of ore.The pulp was diluted and a floating concentrate removed, the unfloatedtailings being discarded.

The concentrate was mixed with saturated brine, diluted to about 10%solids, agitated with slimes of the kind removed in the previousoperation in the amount of 4 lbs. per ton of ore and again floated. Thefloating concentrate consisted of high grade potassium chloride whilethe unfloated solids consisted of lower grade potassium chloride. Thisunfloated material was screened on a 28 mesh screen, yielding a coarsesylvite concentrate and a small amount of finer material, which in acontinuous operation could be returned to the primary flotation cells topass through the system again.

Thus, were recovered 75.7% of the KCl as a high grade concentrate, 13.7%of a lower grade concentrate and 1.6% as a low grade material whichcould be returned to the system for further treatment.

Armac T consists of a mixture of aliphatic amines of the approximatecomposition of 25% mono-n-octadecyl amine acetate, 25% mono-n-hexadecylamine acetate and 50% mono-n-octadecenyl amine acetate.

Example I] This test was carried out in exactly the same manner asExample I except that fullers earth, 4.0 lbs. per ton of feed, wassubstituted for the ore slimes.

The results of this test were as follows 82.7% in the form of high gradematerial and 10.9% as low grade material suitable for fertilizer; theamount and grade of 28 mesh material removed by screening isinsignificant.

Example III In this example again the procedure was exactly the same asin the two foregoing examples except that bentonite, in the amount of 8lbs. per ton of feed was used instead of fullers earth or ore slimes,the results being as follows:

Percent Percent Percent K10 Wt K20 Distribution Feed 100.0 24. 4 100.0High grade concentrate 30. 3 59. 5 73. 8 Coarse Middling (+28 mesh). 7.7 54. 4 17. 2 Fine Middling (28 mesh). 1. 4 19. 2 1. 1 Tailing 60. 6 3.2 7.9

Thus, 73.8% of the KCl was recovered in the form of a high gradeconcentrate and 17.2% as a coarse lower grade product suitable forfertilizer. The amount of low grade product removed by screening wassmall and even if it had not been removed by screening this productwould still contain 48.9% K20, bringing the overall recovery to 92.1%.

Example IV In this example the procedure was the same as in the previousexamples, but the crude sylvinite ore was crushed only to 4 mesh. Thecolloid used was slimes from the sylvinite ore in the amount of 16 lbs.per ton of feed. It was not necessary to screen the unfioated mineralsince it assayed 51.0% K20, the grade commonly used for fertilizingpurposes.

Percent Percent Percent K20 Wt. K20 Distribution Feed 100. 0 24. 4 100.0 High grade fine concentrate. 22. 6 58. 6 54.2 Low grade coarseproduct..- 15. 2 51.0 31. 8 Tailings 62. 2 5. 5 14. 0

Thus, 54.2% of the potash was recovered as a high grade product and31.8% as a coarse fertilizer grade product- I claim:

1. The process of simultaneously recovering a high grade finely dividedsylvite concentrate and a lower grade coarser sylvite concentrate from asylvinite ore which comprises (1) coarsely crushing the crude sylviniteore; (2) mixing the coarsely crushed ore with a substantially saturatedsolution of the soluble constituents of the ore to form a liquidsuspension of the ore; (3) substantially removing slime from the liquidsuspension of the ore; (4) subjecting the deslimed ore to flotationusing as principal reagents a long chain aliphatic amine compound and awater insoluble oil, thereby producing a floating concentrate of thesylvite particles and a tailing principally consisting of halite whichmay be discarded; and (5) refloating the concentrate after agitating itwith an inorganic colloid material thereby obtaining a high grade finelydivided sylvite concentrate as a floating prod not and an unfioatedcoarser product.

2. The process of simultaneously recovering a high grade finely dividedsylvite concentrate and a lower grade coarser sylvite concentrate from asylvinite ore which comprises (1) coarsely crushing the crude sylviniteore; (2) mixing the coarsely crushed ore with a substantially saturatedsolution of the soluble constituents of the ore to form a liquidsuspension of the ore; (3) substantially removing slime from the liquidsuspension of the ore; (4) subjecting the deslimed ore to flotationusing as principal reagents a long chain aliphatic amine compound and awater insoluble oil, thereby producing a floating concentrate of thesylvite particles and a tailing principally consisting of halite whichmay be discarded; (5) refloating the concentrate after agitating it withan inorganic colloid material thereby obtaining a high grade finelydivided sylvite concentrate as a floating product and an unfioatedcoarser product; and (6) screening said unfioated product to obtain acoarse, medium grade product and a low grade finer product which may bediscarded.

3. The process according to claim 1 colloid material is fullers earth.

4. The process according to claim 1 colloid material is bentonite.

5. The process according to claim 1 colloid material is a colloidalclay.

6. The process according to claim 1 which the the the

in which in which in which the colloidal material is a colloidal claypresent in the sylvinite as found in nature.

References Cited in the file of this patent UNITED STATES PATENTSJackson May 13, 1952 Zukosky Jan. 5, 1954

1. THE PROCESS OF SIMULTANEOUSLY RECOVERING A HIGH GRADE FINELY DIVIDEDSYLVITE CONCENTRATE AND A LOWER GRADE COARSER SYLVITE CONCENTRATE FROM ASYLVINITE ORE WHICH COMPRISES (1) COARSELY CRUSHING THE CRUDE SYLVINITEORE; (2) MIXING THE COARSELY CRUSHED ORE WITH A SUBSTANTIALLY SATURATEDSOLUTION OF THE SOLUBLE CONSTITUENTS OF THE ORE TO FORM A LIQUIDSUSPENSION OF THE ORE: (3) SUBSTANTIALLY REMOVING SLIME FROM THE LIQUIDSUSPENSION OF THE ORE; (4) SUBJECTING THE DESLIMED ORE TO FLOTATIONUSING AS PRINCIPAL REAGENTS A LONG CHAIN ALIPHATIC AMINE COMPOUND AND AWATER INSOLUBLE OIL, THEREBY PRODUCING A FLOATING CONCENTRATE OF THESYLVITE PARTICLES AND A TAILING PRINCIPALLY CONSISTING OF HALITE WHICHMAY BE DISCARDED; AND (5) REFLOATING THE CONCENTRATE AFTER AGITATING ITWITH AN INORGANIC COLLOID MATERIAL THEREBY OBTAINING A HIGH GRADE FINELYDIVIDED SYLVITE CONCENTRATE AS A FLOATING PRODUCT AND AN UNFLOATEDCOARSER PRODUCT.